Electrolyte, electrochemical device, and electronic device

Abstract

The present application provides an electrolyte, an electrochemical device, and an electronic device. The electrolyte comprises lithium difluorophosphate, a dinitrile compound, and diethyl carbonate. Based on the total mass of the electrolyte, a mass percentage content of the dinitrile compound is A%, and a mass percentage content of the diethyl carbonate is B%, where 10 ≤ A+B ≤ 24, and 0.8 ≤ A ≤ 3. The present application uses an electrolyte comprising lithium difluorophosphate, a dinitrile compound, and diethyl carbonate, and regulates the values of A+B and A within the above ranges, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

Description

An electrolyte, an electrochemical device, and an electronic device

[0001] This application claims priority to Chinese Patent Application No. 202411837273.1, filed on December 13, 2024, entitled "An Electrolyte, Electrochemical Device and Electronic Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrochemical technology, and in particular to an electrolyte, an electrochemical device, and an electronic device. Background Technology

[0003] With the development of technology, people are paying increasing attention to electrochemical devices widely used in portable electronic devices, electric bicycles, electric vehicles, and energy storage devices, and are pursuing higher operating voltages and energy densities. During charging, gas generation is prone to occur at the internal interfaces of lithium-ion batteries, leading to severe lithium-ion battery expansion and potential safety hazards. At the same time, the high-temperature storage performance and high-temperature cycle performance of lithium-ion batteries face greater challenges. Furthermore, the performance of lithium-ion batteries deteriorates easily at low temperatures, rendering them ineffective; therefore, the low-temperature performance of lithium-ion batteries has also become a key focus. Summary of the Invention

[0004] The purpose of this application is to provide an electrolyte, an electrochemical device, and an electronic device to improve the high-temperature cycling performance, high-temperature storage performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0005] This application provides an electrolyte comprising lithium difluorophosphate, a dinitrile compound, and diethyl carbonate (DEC). Based on the total mass of the electrolyte, the mass percentage of the dinitrile compound is A%, and the mass percentage of the diethyl carbonate is B%, with 10 ≤ A + B ≤ 24 and 0.8 ≤ A ≤ 3. This application uses an electrolyte comprising lithium difluorophosphate, a dinitrile compound, and diethyl carbonate, and controls the values ​​of A + B and A within the aforementioned ranges. During charge and discharge, the chain-like diethyl carbonate can form a stable interface structure between the electrolyte and the positive electrode plate under high voltage with the dinitrile compound containing two cyano groups. Simultaneously, difluorophosphate ions can chelate with diethyl carbonate and the dinitrile compound, uniformly forming a physically and chemically stable interface structure. This stable structure can improve the acid-base environment at the interface, reduce gas generation during charge and discharge reactions, improve the expansion rate of the electrochemical device, and reduce the voltage drop of the electrochemical device at low temperatures, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0006] In some implementations, 12 ≤ A + B ≤ 20. By controlling the value of A + B within this range, the chain-like diethyl carbonate and dinitrile compound can form a more stable interface structure between the electrolyte and the positive electrode during charge and discharge. This structure can further improve the acid-base environment at the interface, inhibit further oxidative decomposition of the electrolyte during charge and discharge, reduce the generation of side reactions and the amount of gas generated during charge and discharge, thereby further improving the expansion rate of the electrochemical device and reducing the voltage drop of the electrochemical device at low temperatures. This further improves the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0007] In some implementations, 15 ≤ A + B ≤ 20. Adjusting the value of A + B within the above range can form a more stable interface structure between the electrolyte and the positive electrode, further improving the expansion rate of the electrochemical device, reducing the voltage drop of the electrochemical device at low temperatures, and improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0008] In some implementations, the mass percentage of lithium difluorophosphate is E%, based on the total mass of the electrolyte, with a value between 0.05 and 2.5%. Adjusting the value of E within this range allows for a more complete chelation effect between difluorophosphate ions and diethyl carbonate and dinitrile compounds, resulting in a more uniformly formed, physically and chemically stable interface structure. This improves the acid-base environment at the interface, further reducing gas generation during the charge-discharge reaction, improving the expansion rate of the electrochemical device, reducing the voltage drop at low temperatures, and enhancing the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0009] In some implementations, 1 ≤ A ≤ 2.4. Controlling the mass percentage A% of the dinitrile compound within the above range helps to form a stable interfacial structure, optimize the acid-base environment at the interface, inhibit further oxidative decomposition of the electrolyte during charge-discharge reactions, reduce the generation of side reactions and gases during charge-discharge, improve the expansion rate of the electrochemical device, and reduce the voltage drop of the electrochemical device at low temperatures, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0010] In some implementations, 10 ≤ B ≤ 20. Controlling the mass percentage of diethyl carbonate (B%) within this range helps to form a stable interfacial structure, optimize the acid-base environment at the interface, inhibit further oxidative decomposition of the electrolyte during charge-discharge reactions, reduce the generation of side reactions and gases during charge-discharge, improve the expansion rate of the electrochemical device, and reduce the voltage drop of the electrochemical device at low temperatures. This also improves the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0011] In some embodiments, the electrolyte further includes propyl propionate, with a mass percentage of propyl propionate of D% based on the total mass of the electrolyte (22 ≤ D ≤ 40). By using an electrolyte including propyl propionate and controlling the D value within the aforementioned range, propyl propionate, dinitrile compounds, and diethyl carbonate can form a high-voltage (>4.45V) stable interfacial structure. This effectively improves the pass rate of hot-box testing of the electrochemical device under high-temperature (>135℃) conditions, effectively reduces gas generation in the electrochemical device during heating, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0012] In some implementations, 30 ≤ D ≤ 40. By controlling the D value within the above range, propyl propionate can form a more stable interfacial structure with dinitrile compounds and diethyl carbonate, which can further improve the pass rate of hot box testing of electrochemical devices under high temperature conditions, further reduce the generation of gas in electrochemical devices during the heating process, and thus further improve the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance and safety performance of electrochemical devices.

[0013] In some embodiments, the dinitrile compound includes butadionitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanoctane, 1,9-dicyanonane, tetramethylbutadionitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanoctane, 2,8-dicyanonane, 1,6-dicyanodecanane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxa-heptanedionitrile, 1,4-di(cyanoethoxy)butane, ethylene glycol di(2-cyano)butane, and ethylene glycol di(cyano)butane. The ethylene glycol di(2-cyanoethyl) ether, diethylene glycol di(2-cyanoethyl) ether, triethylene glycol di(2-cyanoethyl) ether, tetraethylene glycol di(2-cyanoethyl) ether, 1,3-di(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy)butane, ethylene glycol di(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, or 1,6-dicyano-2-methyl-5-methyl-3-hexene. The electrolyte includes dinitrile compounds within the above-mentioned range, which can effectively leverage the interaction between lithium difluorophosphate, dinitrile compounds, and diethyl carbonate to form a stable interface structure between the electrolyte and the positive electrode. This is beneficial for improving the expansion rate of the electrochemical device, reducing the voltage drop of the electrochemical device at low temperatures, and improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0014] In some embodiments, the dinitrile compound includes at least one of adiponitrile or ethylene glycol di(2-cyanoethyl) ether. Dinitrile compounds within the aforementioned range have a certain high-voltage window, enabling preferential oxidation over other components. This facilitates the formation of a more high-voltage-resistant, interface-stable structure, effectively improving the pass rate of hot-box testing of the electrochemical device under high-temperature conditions. Simultaneously, it reduces gas generation in the electrochemical device during heating, thereby enhancing the high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature storage performance of the electrochemical device.

[0015] In some embodiments, the electrolyte also includes a trinitrile compound, with a mass percentage of C% based on the total mass of the electrolyte, where 2.6 ≤ A + C ≤ 3.4%. The electrolyte also includes a trinitrile compound, and the total content (A + C) of the dinitrile and trinitrile compounds is controlled within the aforementioned range. This allows for the formation of a more compact nitrile structure between the relatively stable electron cloud distribution of the dinitrile compound and the relatively unstable electron cloud distribution of the trinitrile compound. This structure can better bind with difluorophosphate ions and diethyl carbonate molecules, inhibiting the decomposition of the positive electrode electrolyte interface (CEI) film at high temperatures, forming a more high-voltage-resistant (>4.45V) stable interfacial structure, and effectively improving the pass rate of the electrochemical device in high-temperature hot-box testing. Simultaneously, it reduces gas generation in the electrochemical device during heating, thereby improving the high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature storage performance of the electrochemical device.

[0016] In some embodiments, the trinitrile compound includes at least one selected from 1,3,6-hexanetrinitrile or 1,3,5-pentanetrinitrile. Using trinitrile compounds of the above types is beneficial for improving the high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature storage performance of electrochemical devices.

[0017] A second aspect of this application provides an electrochemical device, wherein the electrochemical device includes the electrolyte provided in the first aspect of this application.

[0018] In some embodiments, the electrochemical device further includes a separator membrane comprising a base membrane and a porous coating on at least one surface of the base membrane; on the surface of the porous coating, in a 30 μm × 40 μm region, the apparent concentration ratio of oxygen to aluminum is P, where 1 ≤ P ≤ 2.5. By controlling the apparent concentration ratio P of oxygen to aluminum within the aforementioned range, this application can reduce the contact reaction area between the positive and negative electrodes during hot-box testing, thereby improving the hot-box test pass rate. Simultaneously, it can increase the strength of the separator membrane itself, ensuring its permeability is within a suitable range, and improving the electrolyte transport rate. This reduces lithium ion blockage and retention on the separator membrane side, mitigating anode lithium plating, and thus improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature float charge performance of the electrochemical device.

[0019] In some embodiments, the electrochemical device further includes a separator membrane comprising a base film and a porous coating on at least one surface of the base film; the average wall thickness between adjacent pores in the porous coating is T nm, where 25 ≤ T ≤ 450. By controlling the average wall thickness T nm between adjacent pores in the porous coating within the aforementioned range, this application can further improve the electrolyte transport rate, reduce lithium ion retention in localized areas of the separator membrane, reduce expansion of the electrochemical device, and improve the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature float charge performance of the electrochemical device.

[0020] In some embodiments, the electrochemical device further includes a separator membrane comprising a base membrane and a porous coating on at least one surface of the base membrane; the compression rate of the base membrane after compression treatment at 70°C and 2.5 MPa for 40 minutes is Y%, with 25 ≤ Y ≤ 55. This application controls the compression rate Y% of the base membrane after compression treatment at 70°C and 2.5 MPa for 40 minutes to be within the above range, which can further improve the flow of electrolyte in the electrochemical device, reduce the retention of lithium ions in local areas of the separator membrane, reduce the expansion phenomenon of the electrochemical device, and improve the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature float charging performance of the electrochemical device.

[0021] A third aspect of this application provides an electronic device, wherein the electronic device includes the electrochemical device provided in the second aspect of this application.

[0022] This application provides an electrolyte, an electrochemical device, and an electronic device. The electrolyte comprises lithium difluorophosphate, a dinitrile compound, and diethyl carbonate. Based on the total mass of the electrolyte, the mass percentage of the dinitrile compound is A%, and the mass percentage of the diethyl carbonate is B%, with 10 ≤ A + B ≤ 24 and 0.8 ≤ A ≤ 3. This application uses an electrolyte comprising lithium difluorophosphate, a dinitrile compound, and diethyl carbonate, and controls the values ​​of A + B and A within the aforementioned ranges. During charge and discharge, the chain-like diethyl carbonate can form a stable interface structure between the electrolyte and the positive electrode plate under high voltage with the dinitrile compound containing two cyano groups. Simultaneously, the difluorophosphate ions can chelate with the diethyl carbonate and the dinitrile compound to uniformly form a physically and chemically stable interface structure. This stable structure can improve the acid-base environment at the interface, reduce gas generation during the charge and discharge reaction, improve the expansion rate of the electrochemical device, and reduce the voltage drop of the electrochemical device at low temperatures, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device. Detailed Implementation

[0023] The technical solutions of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0024] The first aspect of this application provides an electrolyte comprising lithium difluorophosphate, a dinitrile compound, and diethyl carbonate (DEC), wherein, based on the total mass of the electrolyte, the mass percentage of the dinitrile compound is A%, the mass percentage of the diethyl carbonate is B%, 10≤A+B≤24, and 0.8≤A≤3. For example, A+B can be 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, or a range of any two of these values; A can be 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, or a range of any two of these values. When the value of A is too small, for example, less than 0.8, it is insufficient to improve the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device. When the value of A is too large, for example, greater than 3, it will worsen the interfacial structural stability between the electrolyte and the positive electrode, correspondingly reduce the content of other components in the electrolyte, and worsen the effect of suppressing interfacial gas generation and reducing voltage drop at low temperatures, which is detrimental to improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device. When the value of A+B is too small, for example, less than 10, it is insufficient to improve the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device. When the value of A+B is too large, for example, greater than 24, the excessive content of diethyl carbonate will result in a large amount of diethyl carbonate that is difficult to fully combine with dinitrile compounds, leading to an increase in by-products at the interface, increased gas generation, and worsening of the interfacial structural stability between the electrolyte and the positive electrode, which is detrimental to improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device. This application employs an electrolyte comprising lithium difluorophosphate, a dinitrile compound, and diethyl carbonate, and controls the values ​​of A+B and A within the aforementioned range. During charge and discharge, the chain-like diethyl carbonate can form a stable interface structure between the electrolyte and the positive electrode plate under high voltage with the dinitrile compound containing two cyano groups. Simultaneously, the difluorophosphate ions can chelate with the diethyl carbonate and dinitrile compound, uniformly forming a physically and chemically stable interface structure. This stable structure can improve the acid-base environment at the interface, reduce gas generation during the charge-discharge reaction, improve the expansion rate of the electrochemical device, and reduce the voltage drop of the electrochemical device at low temperatures, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device. In this application, "low temperature" refers to a temperature less than or equal to 0°C.

[0025] In some implementations, 12 ≤ A + B ≤ 20. For example, A + B can be 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, or a range consisting of any two of these values. By controlling the value of A + B within the above range, during charge and discharge, the chain-like diethyl carbonate and dinitrile compound can form a more stable interface structure between the electrolyte and the positive electrode. This structure can further improve the acid-base environment at the interface, inhibit further oxidative decomposition of the electrolyte during charge and discharge, reduce the generation of side reactions and the amount of gas generated during charge and discharge, further improve the expansion rate of the electrochemical device, and reduce the voltage drop of the electrochemical device at low temperatures, thereby further improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0026] In some implementations, 15 ≤ A + B ≤ 20. For example, A + B can be 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, or a range consisting of any two of these values. Adjusting the value of A + B within the above range can create a more stable interface structure between the electrolyte and the positive electrode, further improving the expansion rate of the electrochemical device, reducing the voltage drop at low temperatures, and improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0027] In some implementations, the mass percentage of lithium difluorophosphate is E%, based on the total mass of the electrolyte, and is 0.05 ≤ E ≤ 2.5. For example, E can be 0.05, 0.06, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, or a range of any two of these values. Adjusting the value of E within the above range allows for a more efficient chelation effect between difluorophosphate ions and diethyl carbonate and dinitrile compounds, resulting in a more uniformly formed, physically and chemically stable interface structure. This improves the acid-base environment at the interface, further reducing gas generation during the charge-discharge reaction, improving the expansion rate of the electrochemical device, reducing the voltage drop at low temperatures, and improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0028] In some implementations, 1 ≤ A ≤ 2.4. For example, A can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or a range of any two of these values. Controlling the mass percentage A% of the dinitrile compound within the above range helps to form a stable interfacial structure, optimize the acid-base environment at the interface, inhibit further oxidative decomposition of the electrolyte during charge-discharge reactions, reduce the generation of side reactions and gases during charge-discharge, improve the expansion rate of the electrochemical device, and reduce the voltage drop of the electrochemical device at low temperatures, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0029] In some implementations, 10 ≤ B ≤ 20. For example, B can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or a range of any two of these values. Controlling the mass percentage of diethyl carbonate (B%) within the above range helps to form a stable interfacial structure, optimize the acid-base environment at the interface, inhibit further oxidative decomposition of the electrolyte during charge-discharge reactions, reduce the generation of side reactions and gases during charge-discharge, improve the expansion rate of the electrochemical device, and reduce the voltage drop of the electrochemical device at low temperatures, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0030] In some embodiments, the electrolyte further includes propyl propionate, with a mass percentage of propyl propionate of D% based on the total mass of the electrolyte, 22 ≤ D ≤ 40. For example, D can be 22, 23, 25, 27, 29, 30, 32, 34, 36, 38, 40, or a range of any two of these values. By using an electrolyte that also includes propyl propionate and adjusting the D value within the above range, propyl propionate, dinitrile compounds, and diethyl carbonate can form a high-voltage (>4.45V) stable interfacial structure, which can effectively improve the pass rate of hot-box testing of the electrochemical device under high-temperature (>135°C) conditions, effectively reduce the generation of gas in the electrochemical device during the heating process, thereby improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0031] In some implementations, 30 ≤ D ≤ 40. For example, D can be 30, 32, 34, 36, 38, 40, or a range of any two of these values. By controlling the value of D within the above range, propyl propionate can form a more stable interfacial structure with dinitrile compounds and diethyl carbonate, further improving the pass rate of the electrochemical device in hot-chamber tests under high-temperature conditions, further reducing the generation of gas in the electrochemical device during the heating process, thereby further improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0032] In some embodiments, the dinitrile compound includes butadionitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanoctane, 1,9-dicyanonane, tetramethylbutadionitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanoctane, 2,8-dicyanonane, 1,6-dicyanodecanane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxa-heptanedionitrile, 1,4-di(cyanoethoxy)butane, ethylene glycol di(2-cyano)butane, and ethylene glycol di(cyano)butane. The ethylene glycol di(2-cyanoethyl) ether, diethylene glycol di(2-cyanoethyl) ether, triethylene glycol di(2-cyanoethyl) ether, tetraethylene glycol di(2-cyanoethyl) ether, 1,3-di(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy)butane, ethylene glycol di(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, or 1,6-dicyano-2-methyl-5-methyl-3-hexene. The electrolyte includes dinitrile compounds within the above-mentioned range, which can effectively leverage the interaction between lithium difluorophosphate, dinitrile compounds, and diethyl carbonate to form a stable interface structure between the electrolyte and the positive electrode. This is beneficial for improving the expansion rate of the electrochemical device, reducing the voltage drop of the electrochemical device at low temperatures, and improving the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance of the electrochemical device.

[0033] In some embodiments, the dinitrile compound includes at least one of adiponitrile or ethylene glycol di(2-cyanoethyl) ether. Dinitrile compounds within the aforementioned range have a certain high-voltage window, enabling preferential oxidation over other components. This facilitates the formation of a more high-voltage-resistant, interface-stable structure, effectively improving the pass rate of hot-box testing of the electrochemical device under high-temperature conditions. Simultaneously, it reduces gas generation in the electrochemical device during heating, thereby enhancing the high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature storage performance of the electrochemical device.

[0034] In some embodiments, the electrolyte also includes a trinitrile compound, the mass percentage of which is C% based on the total mass of the electrolyte, and 2.6 ≤ A + C ≤ 3.4. For example, A + C can be 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4 or a range of any two of these values. The electrolyte also includes trinitrile compounds, and the total content (A+C) of dinitrile and trinitrile compounds is controlled within the above-mentioned range. This allows for the formation of a more compact nitrile structure between the relatively stable electron cloud distribution of the dinitrile compounds and the relatively unstable electron cloud distribution of the trinitrile compounds. This structure can better bind with difluorophosphate ions and diethyl carbonate molecules, inhibiting the decomposition of the positive electrode electrolyte interface (CEI) film at high temperatures. This results in a more high-voltage-resistant (>4.45V) stable interfacial structure, effectively improving the pass rate of the electrochemical device in the hot box test under high-temperature conditions. At the same time, it reduces the generation of gas in the electrochemical device during the heating process, thereby improving the high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature storage performance of the electrochemical device.

[0035] In some embodiments, the trinitrile compound includes at least one selected from 1,3,6-hexanetrinitrile or 1,3,5-pentanetrinitrile. Using trinitrile compounds of the above types is beneficial for improving the high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature storage performance of electrochemical devices.

[0036] In some embodiments, in addition to lithium difluorophosphate, the electrolyte also includes other ionizable lithium salts, including at least one selected from LiPF6, LiSbF6, LiAsF6, LiClO4, LiN(C2F5SO2)2, CF3SO3Li, LiC(CF3SO2)3, or LiC4BO8. This application does not particularly limit the content of other ionizable lithium salts, as long as the purpose of this application is achieved. In some embodiments, based on the total mass of the electrolyte, the mass percentage of other ionizable lithium salts is 8% to 15%, preferably 8% to 12%, and more preferably 8% to 10%. If the content of other ionizable lithium salts is too low, for example below 8%, the number of mobile lithium ions in the electrolyte may be insufficient, resulting in reduced high-temperature cycling performance of the electrochemical device. If the content of other ionizable lithium salts is too high, for example above 15%, the viscosity of the electrolyte may increase, causing an increase in electrolyte impedance, resulting in a decrease in lithium ion migration rate and reduced high-temperature cycling performance of the electrochemical device. By controlling the content of other ionizable lithium salts within the above range, a suitable number of mobile lithium ions can be present in the electrolyte, the viscosity of the electrolyte can be kept within a suitable range, the migration rate of lithium ions can be improved, and the high-temperature cycling performance of the electrochemical device can be enhanced.

[0037] In some embodiments, the electrolyte further includes other additives, including at least one of 1,3-propanesulfonate lactone (PS), vinyl sulfate (DTD), or vinylene sulfate (VC); further, other additives include at least one of 4-methylethylene sulfate, 1,4-butanesulfonate lactone (BS), or 1,3-propenesulfonate lactone (PST). This application does not particularly limit the content of other additives, as long as they achieve the purpose of this application. For example, based on the total mass of the electrolyte, the mass percentage of other additives is from 0.2% to 2.5%.

[0038] In some embodiments, the electrolyte also includes fluoroethers. This application does not particularly limit the content of fluoroethers, as long as the purpose of this application is achieved; for example, based on the total mass of the electrolyte, the total mass percentage of fluoroethers is between 0.5% and 4.5%.

[0039] In some embodiments, the electrolyte also includes a non-aqueous solvent. This application does not impose any particular limitation on the non-aqueous solvent, as long as it achieves the purpose of this application. For example, the non-aqueous solvent may include, but is not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents.

[0040] The aforementioned carbonate compounds may include, but are not limited to, at least one of the following: other chain carbonate compounds, cyclic carbonate compounds, or fluorocarbonate compounds, excluding diethyl carbonate. Other chain carbonate compounds may include, but are not limited to, at least one of ethyl propionate (EP), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (EMC). Cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinyl ethylene carbonate (VEC). The aforementioned fluorocarbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, caprolactone, or methyl formate. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. Other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application is achieved. For example, based on the total mass of the electrolyte, the mass percentage of non-aqueous solvents may be 12% to 81%. For example, the mass percentage of non-aqueous solvents can be 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 22%, 25%, 30%, 35%, 40%, 45%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 63%, 65%, 70%, 72%, 73%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, or a range of any two of these values.

[0041] A second aspect of this application provides an electrochemical device, wherein the electrochemical device includes the electrolyte provided in the first aspect of this application. The electrochemical device provided in this application has good high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, and safety performance.

[0042] In some embodiments, the electrochemical device further includes a separating membrane comprising a base film and a porous coating on at least one surface of the base film; on the surface of the porous coating, in a 30 μm × 40 μm region, the apparent concentration ratio of oxygen to aluminum is P, where 1 ≤ P ≤ 2.5. For example, P can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, or a range of any two of these values. In this application, the apparent concentration ratio P of oxygen to aluminum can be controlled by adjusting the mass ratio of inorganic particles to binder in the porous coating. This application controls the apparent concentration ratio P of oxygen to aluminum within the aforementioned range, which effectively ensures a certain coverage of inorganic particles on the separator membrane. This reduces the contact reaction area between the positive and negative electrodes during hot box testing, thereby improving the pass rate of hot box testing. Simultaneously, it enhances the strength of the separator membrane, maintains its permeability within a suitable range, improves the electrolyte transport rate, reduces lithium ion blockage and retention on the separator membrane side, and mitigates anode lithium plating. This, in turn, improves the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature float charging performance of the electrochemical device.

[0043] In some embodiments, the electrochemical device further includes a separating membrane comprising a base film and a porous coating on at least one surface of the base film; the average wall thickness between adjacent pores in the porous coating is T nm, where 25 ≤ T ≤ 450. For example, T can be 25, 40, 50, 70, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 450, or a range of any two of these values. In this application, the average wall thickness T nm between adjacent pores in the porous coating can be controlled by adjusting parameters such as the mass ratio of inorganic particles to binder, the solid content of the porous coating coating solution, the immersion time in the coagulation solution, the drying temperature, and the drying time during the porous coating preparation step. Specifically, increasing the mass ratio of inorganic particles to binder in the porous coating increases T; increasing the solid content of the porous coating coating solution decreases T; increasing the immersion time in the coagulation solution increases T; increasing the drying temperature increases T; and increasing the drying time increases T. This application controls the average wall thickness T nm between adjacent pores in the porous coating. Within the above range, it can further improve the electrolyte transport rate, reduce lithium ion retention in local areas of the separator, reduce the expansion phenomenon of the electrochemical device, and improve the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature float charging performance of the electrochemical device.

[0044] In some embodiments, the electrochemical device further includes a separator membrane, which comprises a base membrane and a porous coating on at least one surface of the base membrane; the compression rate of the base membrane after compression treatment at 70°C and 2.5 MPa for 40 minutes is Y%, 25 ≤ Y ≤ 55. For example, Y can be 25, 30, 35, 40, 45, 50, 55, or a range of any two of these values. In this application, the compression rate Y% of the base membrane after compression treatment at 70°C and 2.5 MPa for 40 minutes can be controlled by adjusting the molecular weight of the base membrane. By controlling the compression rate Y% of the base membrane after compression treatment at 70°C and 2.5 MPa for 40 minutes to be within the above range, this application can further improve the flow of electrolyte in the electrochemical device, reduce the retention of lithium ions in local areas of the separator membrane, reduce the expansion phenomenon of the electrochemical device, and improve the high-temperature storage performance, high-temperature cycling performance, low-temperature discharge performance, safety performance, and high-temperature float charging performance of the electrochemical device.

[0045] In some embodiments, the base membrane of the separator includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. In some embodiments, the base membrane of the separator includes at least one of polyethylene or polypropylene, which has a good effect on preventing short circuits and can improve the safety performance of the electrochemical device through the turn-off effect. This application does not have a particular limitation on the molecular weight of the base membrane, as long as it can achieve the purpose of this application. In some embodiments, the molecular weight of the base membrane is 0.4 × 10⁻⁶. 6 Up to 1.4×10 6 For example, the molecular weight of the base film can be 0.4 × 10⁻⁶. 6 0.5×10 6 0.6×10 6 0.7×10 6 0.8×10 6 0.9×10 6 1.0×10 6 1.1×10 6 1.2×10 6 1.3×10 6 1.4×10 6 Or it can be a range consisting of any two of these values.

[0046] In some embodiments, the porous coating includes first inorganic particles and a binder, wherein the first inorganic particles are selected from at least one of alumina (Al2O3), boehmite, or aluminum hydroxide. This application does not impose any particular limitation on the binder, as long as it achieves the purpose of this application. For example, the binder is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, or polyhexafluoropropylene. The separator membrane using the porous coating of this application can improve the heat resistance, oxidation resistance, and electrolyte wetting properties of the separator membrane, and enhance the adhesion between the separator membrane and the electrode. In some embodiments, the mass ratio of the first inorganic particles to the binder is from 60:40 to 98:2; for example, the mass ratio of the first inorganic particles to the binder can be 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10, 95:5, 98:2, or a range of any two of these values. In some embodiments, the pore diameter of the porous coating of the separator membrane is from 0.01 μm to 1 μm.

[0047] In some embodiments, the preparation steps of the porous coating of the separator membrane include: mixing first inorganic particles and a binder in a mass ratio, then adding a first solvent and stirring evenly to obtain a porous coating solution with a solid content of 5-55 wt%, coating the solution onto the surface of the separator membrane, immersing it in a coagulation solution for 15 to 100 seconds, and then drying it at a temperature of 20°C to 100°C for 0.5 to 6 hours to obtain a separator membrane with a porous coating. This application does not particularly limit the first solvent, as long as it achieves the purpose of this application; for example, the first solvent is N-methylpyrrolidone. This application also does not particularly limit the coagulation solution, as long as it achieves the purpose of this application; for example, the coagulation solution includes a second solvent and a third solvent, and the mass percentage of the second solvent is 30% to 50% based on the total mass of the coagulation solution. For example, the second solvent is N-methylpyrrolidone, and the third solvent is deionized water.

[0048] In some embodiments, the separator further includes an inorganic heat-resistant coating located on at least one surface of the base film. In some embodiments, the inorganic heat-resistant coating is located between the base film and the porous coating. In some embodiments, the inorganic heat-resistant coating includes second inorganic particles and a binder, wherein the second inorganic particles are selected from at least one of alumina (Al2O3), silicon oxide (SiO2), magnesium oxide (MgO), titanium oxide (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium dioxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not impose any particular limitation on the binder, as long as it achieves the purpose of this application; for example, the binder can be at least one of the binders described above. This application does not have a particular limitation on the mass ratio of the second inorganic particles to the binder, as long as the purpose of this application can be achieved. For example, the mass ratio of the second inorganic particles to the binder is 80 to 90: 10 to 20.

[0049] In some embodiments, the separator includes a base film, a first inorganic heat-resistant coating and an organic coating on one surface of the base film, and a second inorganic heat-resistant coating and a porous coating on the other surface of the base film. The first inorganic heat-resistant coating is located between the base film and the organic coating, and the second inorganic heat-resistant coating is located between the base film and the porous coating. In some embodiments, the organic coating includes a high-temperature resistant resin, which includes at least one of a high-melting-point crystalline polymer or a high-temperature resistant amorphous polymer. The high-melting-point crystalline polymer includes at least one of polypropylene, poly(4-methylpentene), polytetrafluoroethylene, or polyvinylidene fluoride, and the high-temperature resistant amorphous polymer includes cyclic olefin copolymers. Based on the mass of the base film, the mass percentage Z% of the high-temperature resistant resin is from 2.5% to 9%. For example, the mass percentage Z% of the high-temperature resistant resin can be 2.5%, 3%, 5%, 7%, 8%, 9%, or a range consisting of any two of these values. Using an organic coating containing the aforementioned high-temperature resistant resin as a separator, and controlling the mass percentage of the high-temperature resistant resin within the aforementioned range, is beneficial for increasing the melt-burst temperature and strength of the separator, and for improving the high-temperature performance of the electrochemical device.

[0050] In some implementations, the thickness of the separator can be from 3 μm to 480 μm.

[0051] In some implementations, the electrochemical device also includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes.

[0052] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The aforementioned "positive active material layer disposed on at least one surface of the positive current collector" means that the positive active material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that the "surface" here can be the entire surface area of ​​the positive current collector or a portion of the surface area; this application does not have any particular limitation, as long as the purpose of this application is achieved. This application does not have any particular limitation on the positive current collector, as long as the purpose of this application is achieved; for example, it can include aluminum foil, aluminum alloy foil, or composite current collectors (e.g., aluminum-carbon composite current collectors). This application does not have any particular limitation on the thickness of the positive current collector and the positive active material layer, as long as the purpose of this application is achieved. For example, the thickness of the positive current collector can be from 1 μm to 200 μm, and the thickness of the positive active material layer can be from 10 μm to 500 μm. It should be understood that these are merely exemplary, and other suitable thicknesses can also be used.

[0053] In some embodiments, the positive electrode active material layer includes a positive electrode active material. This application does not have any particular limitation on the positive electrode active material, as long as it can achieve the purpose of this application. For example, the positive electrode active material may include, but is not limited to, at least one of lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide (e.g., NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, or lithium nickel manganese oxide. In some embodiments, the above-mentioned positive electrode active material may be doped and / or coated.

[0054] In some embodiments, the positive electrode active material layer further includes a positive electrode binder and a positive electrode conductive agent. This application does not particularly limit the types of positive electrode binders and conductive agents, as long as they achieve the purpose of this application. For example, the positive electrode binder may include, but is not limited to, at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, or polyhexafluoropropylene. For example, the positive electrode conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), graphene, carbon nanotubes, or carbon fibers. Conductive carbon black may include, but is not limited to, at least one of acetylene black or Ketjen black. Carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. Carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. This application does not impose any particular restrictions on the mass ratio of positive electrode active material, positive electrode conductive agent, and positive electrode binder in the positive electrode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved.

[0055] In some embodiments, the surface of the positive electrode active material layer further includes a capping layer comprising lithium phosphate and lithium niobate in a mass ratio of 1:3 to 1:1, and the thickness of the capping layer is 1 μm to 1.8 μm.

[0056] In some embodiments, the negative electrode includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector. The phrase "the negative active material layer is disposed on at least one surface of the negative current collector" means that the negative active material layer can be disposed on one surface of the negative current collector along its thickness direction, or on two surfaces of the negative current collector along its thickness direction. It should be noted that "surface" here can be the entire surface area of ​​the negative current collector or a portion of the surface area; this application does not have any particular limitation, as long as the purpose of this application is achieved. This application does not have any particular limitation on the negative current collector, as long as the purpose of this application is achieved; for example, it can contain at least one of copper foil, nickel foil, or carbon-based current collector. This application does not have any particular limitation on the thickness of the negative current collector, as long as the purpose of this application is achieved; for example, the thickness of the negative current collector can be from 1 μm to 200 μm. This application does not have any particular limitation on the thickness of the negative active material layer, as long as the purpose of this application is achieved; for example, the thickness of the negative active material layer can be from 10 μm to 500 μm. It should be understood that these are merely examples, and other suitable thicknesses may also be used.

[0057] In some embodiments, the negative electrode active material layer includes a negative electrode active material. This application does not impose any particular limitation on the negative electrode active material, as long as it can achieve the purpose of this application. For example, the negative electrode active material includes, but is not limited to, at least one of natural graphite, artificial graphite, or silicon-based materials. In some embodiments, the silicon-based material includes at least one of silicon, silicon oxides, silicon carbide compounds, or silicon alloys.

[0058] In some embodiments, the negative electrode active material layer may further include a negative electrode conductive agent and / or a negative electrode binder. This application does not particularly limit the types of negative electrode conductive agents and negative electrode binders, as long as they can achieve the purpose of this application. For example, the negative electrode conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), graphene, carbon nanotubes, or carbon fibers. Conductive carbon black may include, but is not limited to, at least one of acetylene black or Ketjen black. Carbon nanotubes may include, but is not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. Carbon fibers may include, but is not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. For example, the negative electrode binder may include, but is not limited to, at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyacrylate, polyacrylate, polyvinylpyrrolidone, polyimide, polysiloxane, or styrene-butadiene rubber. It should be understood that the above materials are merely exemplary, and the negative electrode active material layer can use any other suitable materials. This application does not particularly limit the mass ratio of the negative electrode active material, negative electrode conductive agent, and negative electrode binder in the negative electrode active material layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application can be achieved. In some embodiments, the mass ratio of negative electrode active material, negative electrode conductive agent and negative electrode binder in the negative electrode active material layer can be (80-99):(0.5-10):(0.5-10). It should be understood that this is only exemplary and is not intended to limit this application.

[0059] The electrochemical device also includes a housing for accommodating the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of electrochemical devices. This application does not limit the scope of these other components. This application does not impose any particular limitation on the housing; it can be a housing known in the art, as long as it achieves the purpose of this application. For example, the housing can be a rigid housing or a flexible housing. The material of the rigid housing can be metal; this application does not limit the type of metal and can use known metal rigid housings, as long as they achieve the purpose of this application. The flexible housing can be a metal-plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0060] In some embodiments, the electrochemical device is a lithium-ion battery, but this application is not limited to this.

[0061] The preparation process of the electrochemical device described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the preparation process of the electrochemical device may include, but is not limited to, the following steps: stacking the positive electrode, the separator, and the negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device. Alternatively, stacking the positive electrode, the separator, and the negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0062] In some implementations, taking lithium-ion batteries as an example, positive electrode sheets, separators, and negative electrode sheets are sequentially wound or stacked into an electrode assembly, which is then placed into a housing such as an aluminum-plastic film, injected with electrolyte, formed, and packaged to produce a lithium-ion battery.

[0063] A third aspect of this application provides an electronic device, wherein the electronic device includes the electrochemical device provided in the second aspect of this application. Therefore, the electronic device provided by this application has good performance. This application does not particularly limit the type of electronic device; it can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0064] Example

[0065] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. A lithium-ion battery is used as an example, but the electrochemical device of this application is not limited to lithium-ion batteries. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" refer to mass measurements.

[0066] Test methods and equipment:

[0067] Low temperature voltage drop test:

[0068] At 25℃, the lithium-ion battery was charged to 4.5V at a constant current of 1C, then charged to 0.05C at a constant voltage, and then discharged to 3.2V at a constant current of 1.5C. After standing for 5 minutes, the voltage was tested. After storing at -20℃ for 30 hours, the voltage was measured again. Low-temperature voltage drop (V) = voltage before storage - voltage after storage.

[0069] Thickness expansion rate test:

[0070] The lithium-ion battery was charged at 65°C with a constant current of 1C to 4.5V, then charged at a constant voltage to a current of 0.05C, and finally discharged at a constant current of 1C to 3V. This constituted the first cycle. The lithium-ion battery was subjected to 20 cycles under these conditions. The thickness of the lithium-ion battery before and after cycling was measured using a height gauge at room temperature. The thickness expansion rate was calculated as follows: Thickness expansion rate (%) = (Thickness after cycling - Thickness before cycling) / Thickness before cycling × 100%.

[0071] 60℃ Cyclic Performance Test:

[0072] The lithium-ion battery underwent its first charge and discharge cycle at 60°C: constant current charging was performed at a charging current of 2C until the full charge voltage of 4.5V was reached; then constant voltage charging was performed at the maximum voltage of 4.5V until the current reached 0.02C; finally, constant current discharging was performed at a discharging current of 0.5C until the final voltage reached 3.0V. The discharge capacity of the first cycle was recorded. This process was repeated for 600 charge and discharge cycles, and the discharge capacity of the 600th cycle was recorded. The 60°C cycle capacity retention rate (%) = (discharge capacity of the 600th cycle / discharge capacity of the first cycle) × 100%.

[0073] High-temperature float charge cycle capacity retention test:

[0074] The lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. It was then charged at a constant current of 1C until the voltage reached 4.5V, and then charged at a constant voltage until the current reached 0.05C. Finally, it was discharged at a constant current of 1C until the voltage reached 3V. The discharge capacity was recorded as the initial discharge capacity of the lithium-ion battery. Afterward, it was charged at a constant current of 0.5C until the voltage reached 4.5V, and then charged at a constant voltage until the current reached 0.05C. The lithium-ion battery was then transferred to a 45°C constant temperature chamber and charged at a constant voltage of 4.5V for 40 days. After 40 days, the lithium-ion battery was transferred to a 25°C constant temperature chamber and left to stand for 60 minutes. It was then discharged at a constant current of 1C until the voltage reached 2.8V. It was then charged at a constant current of 1C until the voltage reached 4.5V, and then charged at a constant voltage until the current reached 0.05C. Finally, it was discharged at a constant current of 1C until the voltage reached 3V. The discharge capacity was recorded as the recoverable capacity of the lithium-ion battery. High-temperature float charge cycle capacity retention rate (%) = (initial discharge capacity - recoverable capacity) / initial discharge capacity × 100%.

[0075] Hot box test:

[0076] The lithium-ion battery was charged at room temperature with a constant current at a rate of 0.5C to a full charge voltage of 4.2V. Charging continued at this constant voltage until a cutoff current of 0.05C was reached, ensuring the battery was fully charged. The battery's appearance was inspected to ensure it was in normal working order. The fully charged battery was then placed in an oven and heated at a rate of 5°C / min until the specified hot-box test temperature of 140°C was reached. This temperature was maintained for one hour, during which the battery's condition was observed. Twenty lithium-ion batteries were used as parallel samples for testing for each example or comparative example. Judgment criteria: The lithium-ion battery did not catch fire or explode. Hot-box test pass rate (%) = (Number of batteries passing the hot-box test / Total number of batteries) × 100%.

[0077] Electrolyte composition testing:

[0078] The electrolyte was obtained by disassembling the lithium-ion battery. The electrolyte components were tested using a gas chromatography-mass spectrometry (GC-MS, model: Agilent GC7890A) and the mass percentage of lithium difluorophosphate, dinitrile compound, diethyl carbonate, propyl propionate, and trinitrile compound was calculated using the external standard method.

[0079] Testing of apparent concentrations of oxygen and aluminum:

[0080] The separator was obtained by disassembling the lithium-ion battery. The surface of the porous coating of the separator was measured by an energy dispersive spectrometer (EDS, model: EDAX Octane SDD). The apparent concentration of oxygen (in wt%) and the apparent concentration of aluminum (in wt%) in a 30μm×40μm region were tested. The ratio of apparent concentration of oxygen to apparent concentration of aluminum, P = apparent concentration of oxygen / apparent concentration of aluminum.

[0081] Testing the average wall thickness between adjacent pores in a porous coating:

[0082] The separator was obtained by disassembling the lithium-ion battery. The 5μm×5μm area of ​​the porous coating of the separator was tested by scanning electron microscopy (SEM), and the wall thickness between every two adjacent holes in 25 evenly distributed adjacent holes was measured. The average wall thickness T nm was calculated.

[0083] Compression ratio test of the base film after compression treatment at 70℃ and 2.5MPa for 40 minutes:

[0084] The separator was obtained by disassembling the lithium-ion battery. The coating on the surface of the separator was scraped off, and the initial thickness H1 of the base film was measured. The base film was compressed at 70°C and 2.5MPa for 40 minutes. The thickness of the base film after the compression treatment was measured as H2. The compression rate Y% = [(H1-H2) / H1]×100%.

[0085] Example 1-1

[0086] <Preparation of the positive electrode>

[0087] Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 97:1:2. N-methylpyrrolidone (NMP) was added, and the mixture was stirred evenly under vacuum to obtain a positive electrode slurry with a solid content of 65 wt%. The positive electrode slurry was uniformly coated onto one surface of a 12 μm thick aluminum foil for the positive electrode current collector. The aluminum foil was dried at 120°C for 1 hour to obtain a positive electrode sheet with a single-sided coating of 80 μm thick positive electrode active material. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode active material. After cold pressing, cutting, and slitting, the sheet was dried under vacuum at 120°C for 1 hour to obtain a positive electrode sheet with dimensions of 74 mm (width) × 867 mm (length), with an empty foil area for the positive electrode current collector at one end along its length.

[0088] Alumina (Dv99 of 0.7 μm) and PVDF binder were mixed at a mass ratio of 80:20, NMP was added, and the mixture was stirred evenly under vacuum to obtain a positive electrode inorganic coating slurry with a solid content of 30 wt%. The positive electrode inorganic coating slurry was uniformly coated onto one surface of the aluminum foil in the empty foil area of ​​the positive current collector at the tail of the positive electrode sheet (this surface is defined as surface a, and the other surface of the positive current collector is defined as surface b). The coating was dried at 120°C for 1 hour to obtain a positive electrode sheet with a positive electrode inorganic coating on surface a of the positive current collector. The length of the positive electrode inorganic coating is 95 mm and the thickness is 2.5 μm.

[0089] <Preparation of Negative Electrode Sheets>

[0090] Artificial graphite (anode active material), conductive carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed in a weight ratio of 96.5:1.5:1:1. Deionized water was added, and the mixture was stirred evenly under vacuum to obtain a cathode slurry with a solid content of 75 wt%. The cathode slurry was uniformly coated onto one surface of a 12 μm thick copper foil current collector and dried at 120 °C to obtain a cathode sheet with a single-sided coating of a 90 μm thick cathode active material layer. The above steps were repeated on the other surface of the copper foil current collector to obtain a cathode sheet with a double-sided coating of cathode active material layer. After cold pressing, cutting, and slitting, a cathode sheet with a size of 76 mm (width) × 874 mm (length) was obtained.

[0091] <Preparation of Electrolyte>

[0092] In an argon-atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC) is first heated to 60°C to convert it into a liquid state. Then, a non-aqueous solvent is prepared according to a mass ratio of ethylene carbonate (EC): ethyl methyl carbonate (EMC): propylene carbonate (PC) = 1:2:1. Next, diethyl carbonate (DEC), propyl propionate, lithium hexafluorophosphate, lithium difluorophosphate, and the dinitrile compound ethylene glycol di(2-cyanoethyl) ether are added and mixed thoroughly to obtain the electrolyte. Based on the total mass of the electrolyte, the mass percentages of lithium hexafluorophosphate are 12.50%, lithium difluorophosphate (E%) are 0.50%, the dinitrile compound (A%) are 0.80%, propyl propionate (D%) are 30.00%, diethyl carbonate (B%) are 15.00%, and the remainder is the non-aqueous solvent.

[0093] <Preparation of the separating membrane>

[0094] A material with a thickness of 10 μm and a molecular weight of 1.3 × 10⁻⁶ was used. 6 Polyethylene (PE) microporous membrane (provided by Shanghai Enjie Co., Ltd.) is used as the base membrane for the isolation membrane. One surface of the base membrane is defined as the c-surface, and the other surface is defined as the d-surface.

[0095] Preparation of the coating on the c-side of the separator:

[0096] Inorganic boehmite particles with a Dv50 of 1.1 μm were mixed with polyacrylate at a mass ratio of 85:15 and dissolved in deionized water to form an inorganic heat-resistant coating slurry with a solid content of 47 wt%. The resulting inorganic heat-resistant coating slurry was then uniformly coated onto one surface of a PE base film using a microgravure coating method and dried in an oven at 120 °C to obtain a release film with an inorganic heat-resistant coating of 1.8 μm thickness on the c-side.

[0097] Polypropylene (PP), the first polymer, was added to a stirrer and stirred until homogeneous. Sodium carboxymethyl cellulose was added to the stirrer and stirred until homogeneous. Dimethylsiloxane, the wetting agent, was added to the stirrer, followed by deionized water and stirring. The viscosity of the slurry was adjusted to 45 mPa·s and the solid content to 6 wt%, resulting in an organic coating slurry. The organic coating slurry was uniformly coated onto the surface of the inorganic heat-resistant coating on the c-side of the release liner. After drying in an oven at 120°C, a release liner with a 3 μm thick organic coating and a 1.8 μm thick inorganic heat-resistant coating on the c-side was obtained. The mass ratio of the first polymer, sodium carboxymethyl cellulose, and dimethylsiloxane was 95:0.5:4.5.

[0098] Preparation of the coating on the d-side of the isolation membrane:

[0099] Inorganic boehmite particles with a Dv50 of 1.1 μm were mixed with polyacrylate at a mass ratio of 85:15 and dissolved in deionized water to form an inorganic heat-resistant coating slurry with a solid content of 47 wt%. The resulting inorganic heat-resistant coating slurry was then uniformly coated onto another surface of a PE base film using a microgravure coating method and dried in an oven at 120 °C to obtain a release film with an inorganic heat-resistant coating of 1.8 μm thickness on the d side.

[0100] Inorganic boehmite particles and polyvinylidene fluoride binder were mixed at a mass ratio of M1:M2 = 85:15, and then N-methylpyrrolidone (first solvent) was added and stirred evenly to obtain a porous coating liquid with a solid content of 8 wt%. The porous coating liquid was applied to the surface of the inorganic heat-resistant coating on the d side of the separator membrane using an immersion coating method to form a wet film. The separator membrane with the wet film was then immersed in a coagulation medium containing deionized water (third solvent) and N-methylpyrrolidone (second solvent). Phase transformation occurs in the liquid. After immersion in the coagulation solution for 30 seconds, the membrane is placed in an oven and dried at 60°C for 2 hours to obtain a separating membrane with a porous coating of 3 μm thickness and an inorganic heat-resistant coating of 1.8 μm thickness on the d side, and an organic coating of 3 μm thickness and an inorganic heat-resistant coating of 1.8 μm thickness on the c side. The mass percentage of N-methylpyrrolidone (second solvent) in the coagulation solution is 38%, and the remainder is the third solvent. The temperature of both the porous coating application solution and the coagulation solution is 25°C.

[0101] <Preparation of Lithium-ion Batteries>

[0102] The positive electrode, separator, and negative electrode prepared above are stacked in sequence, with the separator acting as a separator between the positive and negative electrode. The a-side of the positive electrode faces the d-side of the separator. The electrode assembly is then wound up to form an electrode assembly. After welding the tabs, the electrode assembly is placed in an outer aluminum-plastic film. After removing moisture at 80°C, the electrolyte is injected. The battery undergoes vacuum sealing, settling, formation (with an upper limit voltage of 4.5V, a formation temperature of 70°C, and a settling time of 2 hours), shaping, and capacity testing to obtain a lithium-ion battery.

[0103] Examples 1-2 to Examples 1-30

[0104] Except for adjusting the mass percentages of dinitrile compound A%, diethyl carbonate B%, type of dinitrile compound, and lithium difluorophosphate E as shown in Table 1 in the <Preparation of Electrolyte>, the mass percentages of non-aqueous solvents are changed accordingly, the mass percentages of propyl propionate and lithium hexafluorophosphate remain unchanged, the rest are the same as in Examples 1-1.

[0105] Examples 2-1 to 2-13

[0106] Except for the addition of propyl propionate and / or trionitrile compound 1,3,6-hexanetrionitrile as shown in Table 2 in the <Preparation of Electrolyte>, and the adjustment of the mass percentage of propyl propionate D%, the mass percentage of trionitrile C, the mass percentage of non-aqueous solvent, the mass percentage of dionitrile, the mass percentage of diethyl carbonate, the mass percentage of lithium hexafluorophosphate, and the mass percentage of lithium difluorophosphate as shown in Table 2, the rest is the same as in Examples 1-2.

[0107] Examples 3-1 to 3-12

[0108] Except for adjusting the corresponding preparation parameters as shown in Table 3 in the <Preparation of the Separating Membrane> section, such that the apparent concentration ratio of oxygen to aluminum P, the average wall thickness T nm between adjacent pores in the porous coating, and the compression ratio Y% of the base film after compression treatment at 70°C and 2.5 MPa for 40 minutes are as shown in Table 3, the rest are the same as in Examples 1-2.

[0109] Comparative Examples 1-1 to 1-6

[0110] Except for adjusting the mass percentages of dinitrile compound A%, diethyl carbonate B%, and lithium difluorophosphate E according to Table 1 in the <Preparation of Electrolyte>, the mass percentages of non-aqueous solvents are changed accordingly, while the mass percentages of propyl propionate and lithium hexafluorophosphate remain unchanged. The rest is the same as in Examples 1-1.

[0111] Table 1

[0112] Note: " / " in Table 1 indicates that there are no corresponding preparation parameters.

[0113] Table 2

[0114] Note: In Table 2, " / " indicates that there are no corresponding preparation parameters.

[0115] As can be seen from Examples 1-1 to 1-30 and Comparative Examples 1-1 to 1-6, when the electrolyte includes lithium difluorophosphate, dinitrile compound, and diethyl carbonate, and the values ​​of the dinitrile compound content A and the total content of dinitrile compound and diethyl carbonate A+B are controlled within the scope of this application, the lithium-ion battery has a lower thickness expansion rate, a lower low-temperature voltage drop, a higher high-temperature cycle capacity retention rate, and a higher hot box test pass rate, indicating that the lithium-ion battery has good safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance.

[0116] The value of lithium difluorophosphate content E affects the safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 1-2, 1-23 to 1-30, when the value of E is adjusted within the range of this application, the lithium-ion battery exhibits a lower thickness expansion rate, a lower low-temperature voltage drop, a higher high-temperature cycle capacity retention rate, and a higher hot box test pass rate, indicating that the lithium-ion battery has good safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance.

[0117] The content of dinitrile compound A and / or diethyl carbonate content B affects the safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 1-1 to 1-20, when the values ​​of A and / or B are adjusted within the range of this application, the lithium-ion battery exhibits a lower thickness expansion rate, a lower low-temperature voltage drop, a higher high-temperature cycle capacity retention rate, and a higher hot box test pass rate, indicating that the lithium-ion battery has good safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance.

[0118] The type of dinitrile compound affects the safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 1-2, 1-21, and 1-22, lithium-ion batteries using dinitrile compounds within the scope of this application exhibit lower thickness expansion, lower low-temperature voltage drop, higher high-temperature cycle capacity retention, and higher hot box test pass rate, indicating that the lithium-ion batteries possess good safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance.

[0119] The content (D) of propyl propionate affects the safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 1-2 and 2-1 to 2-7, by using an electrolyte that also includes propyl propionate and controlling the propyl propionate content (D) within the scope of this application, the lithium-ion battery exhibits a lower thickness expansion rate, a lower low-temperature voltage drop, a higher high-temperature cycle capacity retention rate, and a higher hot box test pass rate, indicating that the lithium-ion battery has good safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance.

[0120] The total content (A+C) of dinitrile and trinitrile compounds affects the safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 2-1, 2-8 to 2-13, by using an electrolyte that also includes trinitrile compounds and adjusting the total content (A+C) of dinitrile and trinitrile compounds within the scope of this application, the lithium-ion battery exhibits a lower thickness expansion rate, a lower low-temperature voltage drop, a higher high-temperature cycle capacity retention rate, and a higher hot box test pass rate, indicating that the lithium-ion battery has good safety performance, low-temperature discharge performance, high-temperature cycle performance, and high-temperature storage performance.

[0121] The apparent concentration ratio (P) of oxygen to aluminum in the porous coating of the separator, the average wall thickness (T) between adjacent pores in the porous coating, and the compression ratio (Y) of the separator base film after compression treatment at 70°C and 2.5 MPa for 40 minutes affect the safety performance, low-temperature discharge performance, high-temperature cycle performance, high-temperature storage performance, and high-temperature float charge performance of lithium-ion batteries. As can be seen from Examples 1-2 and 3-1 to 3-12, lithium-ion batteries with adjusted values ​​of P, T, and Y within the scope of this application exhibit lower thickness expansion rate, lower low-temperature voltage drop, higher high-temperature cycle capacity retention rate, higher hot box test pass rate, and higher high-temperature float charge cycle capacity retention rate, indicating that the lithium-ion batteries possess good safety performance, low-temperature discharge performance, high-temperature cycle performance, high-temperature storage performance, and high-temperature float charge performance.

[0122] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0123] The element connected by the terms "one of," "among," "a kind of," or other similar terms refers to any one of the listed elements. For example, "one of A or B" means only A or only B; similarly, "one of A, B, and C" means only A, only B, or only C. The element connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms refers to any combination of the listed elements. For example, "at least one of A or B" means only A, only B, A and B; similarly, "at least one of A, B, or C" means only A, only B, only C, only A and B, only A and C, only B and C, A and B and C.

[0124] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0125] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrolyte, wherein, The electrolyte comprises lithium difluorophosphate, a dinitrile compound, and diethyl carbonate. Based on the total mass of the electrolyte, the mass percentage of the dinitrile compound is A%, the mass percentage of the diethyl carbonate is B%, 10≤A+B≤24, and 0.8≤A≤3.

2. The electrolyte according to claim 1, wherein, 12≤A+B≤20.

3. The electrolyte according to claim 1, wherein, 15≤A+B≤20.

4. The electrolyte according to claim 1, wherein, Based on the total mass of the electrolyte, the mass percentage of lithium difluorophosphate is E%, where 0.05 ≤ E ≤ 2.

5.

5. The electrolyte according to claim 1, wherein, The electrolyte satisfies at least one of the following characteristics: a) 1 ≤ A ≤ 2.4; b) 10 ≤ B ≤ 20.

6. The electrolyte according to any one of claims 1 to 5, wherein, The electrolyte also includes propyl propionate, and the mass percentage of propyl propionate is D% based on the total mass of the electrolyte, with 22 ≤ D ≤ 40%.

7. The electrolyte according to claim 6, wherein, 30≤D≤40。 8. The electrolyte according to any one of claims 1 to 5, wherein, The dinitrile compounds include succinic anionyl nitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanoctane, 1,9-dicyanonane, tetramethylsuccinic anionyl nitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanoctane, 2,8-dicyanonane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxa-heptanenitrile, 1,4-di(cyanoethoxy)butane, and ethylene glycol di(2-cyanoethyl). The ether, diethylene glycol di(2-cyanoethyl) ether, triethylene glycol di(2-cyanoethyl) ether, tetraethylene glycol di(2-cyanoethyl) ether, 1,3-di(2-cyanoethoxy)propane, 1,4-di(2-cyanoethoxy)butane, ethylene glycol di(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4-dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, or at least one of 1,6-dicyano-2-methyl-5-methyl-3-hexene.

9. The electrolyte according to claim 8, wherein, The dinitrile compound includes at least one of adiponitrile or ethylene glycol di(2-cyanoethyl) ether.

10. The electrolyte according to any one of claims 1 to 5, wherein, The electrolyte also includes a trinitrile compound, and the mass percentage of the trinitrile compound is C% based on the total mass of the electrolyte, with 2.6 ≤ A + C ≤ 3.

4.

11. An electrochemical device, wherein, The electrochemical device includes the electrolyte according to any one of claims 1 to 10.

12. The electrochemical device according to claim 11, wherein, The electrochemical device further includes a separating membrane, the separating membrane comprising a base membrane and a porous coating located on at least one surface of the base membrane; the separating membrane satisfies at least one of the following characteristics: x) On the surface of the porous coating, in a 30μm×40μm region, the apparent concentration ratio of oxygen to aluminum is P, where 1≤P≤2.

5. y) The average wall thickness between adjacent pores in the porous coating is T nm, where 25 ≤ T ≤ 450; z) The compression rate of the base film after compression treatment at 70°C and 2.5 MPa for 40 minutes is Y%, 25≤Y≤55.

13. An electronic device, wherein, The electronic device includes the electrochemical device according to any one of claims 11 to 12.

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